Java BsonReader.readNull方法代码示例

import org.bson.BsonReader; //导入方法依赖的package包/类
public void decode(BsonReader reader, T instance, DecoderContext decoderContext) {
    LOGGER.debug("Decode field : " + getMappedFieldName() + " Signature: " + fieldTypePair.getRealType());
    if (field.getType().isPrimitive()) {
        if (reader.getCurrentBsonType() == BsonType.NULL || reader.getCurrentBsonType() == BsonType.UNDEFINED) {
            reader.skipValue();
        } else {
            primitiveType.decode(reader, instance, decoderContext, this);
        }
    } else if (codec != null) {
        if (reader.getCurrentBsonType() == BsonType.NULL ) {
            reader.readNull();
            setFieldValue(instance, null);
        }
        else if (reader.getCurrentBsonType() == BsonType.UNDEFINED) {
            reader.skipValue();
        }
        else {
            F decoded = codec.decode(reader, decoderContext);
            setFieldValue(instance, decoded);
        }
    }
}
 

import org.bson.BsonReader; //导入方法依赖的package包/类
private Object readValue(final BsonReader reader, final DecoderContext decoderContext) {
    BsonType bsonType = reader.getCurrentBsonType();
    if (bsonType == BsonType.NULL) {
        reader.readNull();
        return null;
    } else if (bsonType == BsonType.ARRAY) {
        return readList(reader, decoderContext);
    } else if (bsonType == BsonType.BINARY && BsonBinarySubType.isUuid(reader.peekBinarySubType()) && reader.peekBinarySize() == 16) {
        return codecRegistry.get(UUID.class).decode(reader, decoderContext);
    }
    return bsonTypeCodecMap.get(bsonType).decode(reader, decoderContext);
}
 

import org.bson.BsonReader; //导入方法依赖的package包/类
@Override
public T decode(BsonReader reader, DecoderContext decoderContext) {
    if (reader.getCurrentBsonType() == BsonType.NULL) {
        reader.readNull();
        return null;
    }

    String discriminator = null;
    reader.mark();
    reader.readStartDocument();
    PolymorphicCodec<T> codec = null;
    while (reader.readBsonType() != BsonType.END_OF_DOCUMENT) {
        String fieldName = reader.readName();
        if (allDiscriminatorKeys.contains(fieldName)) {
            discriminator = reader.readString();
            codec = getCodecForDiscriminator(discriminator);
            if (codec != null) {
                //now check that the codec found actually has the correct
                String discriminatorKeyForClass = discriminatorKeys.get(codec.getEncoderClass());
                if (fieldName.equals(discriminatorKeyForClass)) {
                    break;
                } else {
                    discriminator = null;
                    codec = null;
                    LOGGER.warn("Confusing. Skipping discriminator {} encoded in discriminator key {} since the " +
                                    "destination class is declaring a different discriminator key {}.",
                            discriminator, fieldName, discriminatorKeyForClass);
                }
            }
        } else {
            reader.skipValue();
        }
    }

    reader.reset();

    // try fallback and legacy handling
    if (codec == null) {
        if (discriminator != null) {
            LOGGER.warn("At least one valid discriminator {} was found in database, but no matching codec found at all.", discriminator);
            reader.skipValue();
            return null; // todo: when switching to mongo db 3.6 an exception should be thrown instead of returning null
        }
        LOGGER.debug("No discriminator found in db for entity. Trying fallback. Fallback is {}", fallBackCodec);
        codec = fallBackCodec;
        if (codec == null) {
            LOGGER.debug("FallbackCodec is null. Still no matching codec found for discriminator {} within discriminatorToCodec {}", discriminator, discriminatorToCodec);
            if (classToCodec.values().size() == 1) {
                codec = classToCodec.values().iterator().next();
                LOGGER.debug("Found single possible codec {} for type {}", codec, getEncoderClass());
            }
            else {
                LOGGER.warn("Legacy handling to resolve entities in db without discriminator failed as there are (now?) more than one codecs available {}. One option is to use @DiscriminatrFallback at the legacy class or to add discriminators to the entities within the database. For now, skipping value.", classToCodec);
                // TODO is skipping the right way to handle this? This might lead to lost data if a read object is rewritten to the database again...
                reader.skipValue();
                return null;// todo: when switching to mongo db 3.6 an exception should be thrown instead of returning null
            }
        }
    }


    return decodeWithType(reader, decoderContext, codec);
}